Which OTP behavior should I use for an “endless” repetition of tasks?

Question:

I want to repeatedly run the same sequence of operations over and over again next to a Phoenix application (without crashing the whole web-app if something brakes in the worker of course) and don't really know wether I should use a GenServer, Elixir's Tasks, an Agent or something completely different I haven't thought about so far.

When I start my Phoenix app a worker should start as well, that periodically pulls some values of a serial-connection, broadcasts them through a Phoenix channel, collects them until @save_interval is reached and then calculates the median, broadcasts that median via a different channel and writes it to an InfluxDB. Right now I have something (kind of working) like this:

I'm only starting to figure all that OTP stuff out and hope someone of you could help me stumble into the right direction here.

Answer:

You should use a GenServer that sends itself messages after x seconds (60 seconds in the example below):

defmodule MyApp.Worker do
use GenServer
def start_link() do
GenServer.start_link(__MODULE__, [])
end
def init([]) do
schedule_work()
{:ok, []}
end
def handle_info(:work, state) do
state = do_work(state)
schedule_work()
{:noreply, state}
end
defp do_work(state) do
# Do your work here and return state
end
defp schedule_work do
Process.send_after(self(), :work, 60_000)
end
end

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